I just been on a claim survey to find out what is causing defrost heaters to fails from evaporators,thus accumulating ice. I found that besides the normal defrost timer,there is also defrost thermistor to stop short the defrost cycle once evaporator is clear. I found that both evaporator fan motors switch Off when set temperature is reached. I discussed with on site tech and se set fans to run continuously,except during defrost. what may be the cause of repetitive failure of defrost heaters ? I still have to inspect some of the replaced when they find them !! Heaters may fail open or shorted through insulation. what causes what ?
Any suggestions please ?